1. Field of the Invention
The present invention relates to a method of preparing metal nanocomposites, and particularly, to a method of preparing nanocomposites using reactive ball milling of metal powders under hydrogen pressure.
2. Description of the Related Art
Owing to the dramatic global environmental changes associated with man-made carbon dioxide emissions and the huge consumption of the limited resources of fossil fuels, developing alternate energy sources is important for a sustainable future. The increase in threats from global warming due to the consumption of fossil fuels requires our planet to adopt new strategies to harness the inexhaustible sources of energy. Hydrogen is an energy carrier, which holds tremendous promise as a new clean energy option. It is a convenient, safe, versatile fuel source that can be easily converted to a desired form of energy without releasing harmful emissions. A key advantage of hydrogen is that when burned, carbon dioxide (CO2) is not produced.
Magnesium (Mg) and Mg-based materials can store hydrogen in a solid-state matter. The natural abundance, cheap price, operational cost effectiveness, light weight, and high hydrogen storage capacity (7.60 wt. %, 0.11 kg H2L−1) are some advantages of Mg and Mg-based alloys that make them desirable storage materials for research and development. Since 1991, nanocrystalline MgH2 powders have been successfully produced near room temperature by reactive ball milling technique (RBM) using a high-energy ball mill operated at hydrogen atmospheric pressure.
There are some major drawbacks found in conventional MgH2 systems, however. Firstly, MgH2 shows a high thermal stability making the hydrogen releasing at moderate. temperatures (below 400° C.) very difficult. Secondly, MgH2 exhibits very slow kinetics of hydrogenation/dehydrogenation at temperatures less than 400° C. Thus, innumerable efforts have been tackled to improve the kinetics behavior of MgH2 by catalyzing the metal hydride powders with wide spectrum of mono, binary and multicatalytic systems. One such effort involved catalyzing the MgH2 powders by ball milling with transition metal powders of Ti, V, Mn, Fe and Ni. In another work, MgH2 powders were catalyzed by a small amount (1 mol. %) of Fe, Co, Ni and Cu nanoparticles. The mechanically doped MgH2/Ni powders obtained after a very short milling time (2 h).
Thus, a method of synthesizing metal nanocomposites using reactive high energy ball milling (RBM) process thereby solving the aforementioned problems is desired.